studio-backend-python

A set of instructions for working on the Python backend of Junjo AI Studio, including its FastAPI web routes, services, repositories, SQLite database use, and tests.

In plain words
What is it for?
Use it when changing or reviewing Studio backend code, database access, data-processing coordination, API behavior, backend tests, or related scripts.
Why use it?
It keeps backend changes aligned with the project's existing code organization, database rules, API behavior, and testing practices.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/mdrideout/junjo/studio-backend-python
Any agent
npx skills add mdrideout/junjo --skill studio-backend-python
Clone the repo
git clone --depth 1 https://github.com/mdrideout/junjo

Made for: Claude Code, Codex.

Per session 41 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 552 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00041 $0.00552
Opus 5 $0.00020 $0.00276
Sonnet 5 $0.00008 $0.00110
Haiku 4.5 $0.00004 $0.00055

Measured yesterday against content hash 5b2106f116c7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

studio-backend-python scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/studio-backend-python/SKILL.md · 58 lines

How it starts

The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Studio Backend Python

Use This Skill When

  • The task touches apps/studio/backend/app/, apps/studio/backend/migrations/, or apps/studio/backend/conftest.py.
  • The task changes FastAPI endpoints, Pydantic schemas, services, repositories, SQLite usage, DataFusion orchestration, or backend-visible ingestion query behavior.
  • The task changes backend tests, scripts, or organization.

Do Not Use This Skill When

  • The task is primarily ingestion runtime flow work.
  • The task is primarily frontend UI or state work.
  • The task is primarily an authentication review better handled by studio-security-auth.

Workflow

  1. Read apps/studio/AGENTS.md, then start from the touched code and nearest tests.
  2. Use owner docs only where they constrain the work:
    • apps/studio/backend/app/db_sqlite/README.md
    • apps/studio/TESTING.md
    • apps/studio/ingestion/adr/002-sqlite-metadata-index.md for indexing and recent-cold bridge invariants
    • apps/studio/ingestion/adr/001-segmented-wal-architecture.md for hot snapshot or WAL semantics
    • apps/studio/docs/adr/004-events-json-contract.md for events_json
  3. Keep backend code explicit and single-purpose.
  4. Follow the scoped runtime rules: no legacy fallbacks and no hand-edited Alembic migrations.
  5. Pair with studio-ingestion-flow when changing query bridging, proto contracts, or hot-snapshot behavior.
  6. Pair with studio-security-auth when changing an authentication trust boundary, middleware order, cookie policy, or API-key validation.
  7. Keep ADRs strategic and update the owning document only.
  8. Never access a running backend container's bind-mounted SQLite database or WAL from a host process. apps/studio/TESTING.md owns the stopped-stack reset procedure.

Validation

Run the smallest relevant checks from apps/studio:

  • ./backend/scripts/run-backend-tests.sh
  • cd backend && uv run ruff check app/
  • ./backend/scripts/validate_rest_api_contracts.sh when REST contracts change

Read the full file on GitHub · 58 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 58 lines · 41 tokens per session scan A 5b2106f116c7

Subscribe to this mod's changes

studio-backend-python is a skill published in the GitHub repository mdrideout/junjo (20 stars, last pushed yesterday), licensed Apache-2.0. It adds 41 tokens to every session and 552 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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